DESCRIPTION (Applicant's Abstract): The long-term focus is the control over pattern as exersized by Organizers. In the Drosophila embryo, adjacent rows of cells flanking each parasegment secrete two organizing signals, Wingless and Hedgehog. These two signals are responsible for assigning cell fates across the remainder of the parasegment, and these signals act asymmetrically from the organizing center. The aims of this proposal focus on genes involved in Wingless signaling from the organizer. Both cell culture and transgenic approaches are outlined for arrow, which encodes a novel Wg signal transducer. The experiments will determine whether the Arrow transmembrane protein binds directly to Wingless, or complexes with the Frizzled proteins as a co-receptor. Intracellularly, yeast two-hybrid studies, as well as cell culture and in vitro analysis are proposed to explore how Arrow transduces the Wingless signal. Analogous two hybrid and in vivo studies will determine how lines, which encodes a stage-specific factor regulating the response to Wg, interacts with known or novel Wg signal transducers. Response elements in defined Wingless target genes will be studied to identify how signal integration is achieved as the organizer operates. Finally, two genetic screens are proposed to identify novel components that either interact with Arrow or Lines, or control organizer asymmetry.